Self-confined catalytic DNA circuit for on-site nonenzymatic amplified microRNA imaging.

MicroRNAs (miRNAs) are critical regulators in cancer biology, yet their low abundance and high sequence similarity pose significant challenges for accurate intracellular detection. Herein, we present a metal-organic frameworks (MOFs) with self-confined catalytic DNA circuit (designated as MSCDC) integrated within a pH-responsive MIL-53(Fe) framework for on-site, nonenzymatic amplified imaging of miRNA-9 in hepatocellular carcinoma (HCC) cells. The MSCDC was synthesized by anchoring double-stemmed DNA hairpin probes onto MIL-53(Fe) through π-π stacking and electrostatic interactions, achieving high probe density and nuclease resistance. The pH-triggered degradation of MIL-53(Fe) facilitated efficient intracellular release of DNA probes, while the self-confined catalytic DNA circuit enabled autonomous, enzyme-free amplification, converting weak miRNA-9 inputs into strong fluorescence outputs. Compared with conventional carriers, the MSCDC exhibited superior probe loading capacity, enhanced serum stability, excellent biocompatibility, and a femtomolar detection limit (0.32 fM). Importantly, the nanoplatform enabled reliable, real-time visualization of oncogenic miRNA-9 in diverse HCC cell lines, yielding results that were highly consistent with qRT-PCR. This work highlights a generalizable self-confined, nonenzymatic nucleic acid amplification strategy for precise intracellular biosensing, thereby opening avenues for early cancer diagnosis and molecular imaging.